Faculty of Psychology and Educational Sciences (FPSE), University of Geneva, Geneva, Switzerland.
Cognitive Sciences, Department of Linguistics, University of Potsdam, Potsdam, Germany.
Psychophysiology. 2018 Feb;55(2). doi: 10.1111/psyp.12982. Epub 2017 Aug 28.
Electrophysiological research using verbal response paradigms faces the problem of muscle artifacts that occur during speech production or in the period preceding articulation. In this context, this paper has two related aims. The first is to show how the nature of the first phoneme influences the alignment of the ERPs. The second is to further characterize the EEG signal around the onset of articulation, both in temporal and frequency domains. Participants were asked to name aloud pictures of common objects. We applied microstate analyses and time-frequency transformations of ERPs locked to vocal onset to compare the EEG signal between voiced and unvoiced labial plosive word onset consonants. We found a delay of about 40 ms in the set of stable topographic patterns for /b/ relative to /p/ onset words. A similar shift was observed in the power increase of gamma oscillations (30-50 Hz), which had an earlier onset for /p/ trials (∼150 ms before vocal onset). This 40-ms shift is consistent with the length of the voiced proportion of the acoustic signal prior to the release of the closure in the vocal responses. These results demonstrate that phonetic features are an important parameter affecting response-locked ERPs, and hence that the onset of the acoustic energy may not be an optimal trigger for synchronizing the EEG activity to the response in vocal paradigms. The indexes explored in this study provide a step forward in the characterization of muscle-related artifacts in electrophysiological studies of speech and language production.
使用言语反应范式的电生理研究面临着在言语产生期间或在发音之前发生的肌肉伪影的问题。在这种情况下，本文有两个相关的目的。第一个目的是展示第一个音素的性质如何影响 ERP 的对齐。第二个目的是进一步描述发音起始时的 EEG 信号，包括在时域和频域内。参与者被要求大声说出常见物体的图片。我们应用微状态分析和与发声起始锁定的 ERP 的时频变换，比较浊音和清音唇塞音起始辅音的 EEG 信号。我们发现，相对于 /p/ 起始词，/b/ 起始词的稳定拓扑模式集延迟了约 40ms。在 30-50Hz 的伽马振荡（gamma oscillations）的功率增加中观察到类似的变化，其在 /p/ 试验中的起始时间更早（在发声起始前约 150ms）。这个 40ms 的偏移与发声信号中闭合释放前浊音比例的长度一致。这些结果表明，语音特征是影响反应锁定 ERP 的重要参数，因此，声能的起始可能不是将 EEG 活动与发声范式中的反应同步的最佳触发点。本研究中探索的指标在语音和语言产生的电生理研究中肌肉相关伪影的特征化方面迈出了一步。
